1. Field of the Invention
The present invention relates to the field of turbomachines and more particularly to a turbomachine combustion chamber.
2. Description of the Related Art
In the description below, the terms “upstream” and “downstream” are used to designate the positions of structural elements relative to one another in an axial direction, taking the gas flow direction as a reference. Similarly, the terms “inner” or “radially inner” and “outer” or “radially outer” are used to designate the positions of structural elements relative to one another in a radial direction, using the axis of symmetry of the structure in question as a reference.
A turbomachine comprises one or more compressors delivering air under pressure to a combustion chamber where the air is mixed with fuel and ignited so as to generate hot combustion gas. This gas flows downstream from the chamber towards one or more turbines that transform the energy received in this way so as to drive the compressor(s) in rotation and also provide the work that is needed, e.g. for powering an airplane.
Typically, an annular combustion chamber used in aviation comprises inner and outer longitudinal walls forming surfaces of revolution that are connected together at their upstream ends by an annular transverse wall referred to as the chamber end wall. The chamber end wall has a plurality of circumferentially spaced-apart openings, each receiving an injector device having an injector positioned in the middle thereof, the end wall and the injector together enabling the mixture of air and fuel to be delivered for being burnt in the combustion chamber.
The combustion chamber is fed with liquid fuel mixed with air coming from a compressor. The liquid fuel is taken to the combustion chamber by injectors in which it is vaporized into fine droplets. Vaporization is initiated in the injectors by means of nozzles and it continues in a Venturi and a pre-vaporization bowl under the effect of the air under pressure coming from a compressor. This air under pressure passes firstly through radial swirlers of the injector device in order to set the fuel sprayed by the injector into rotation, and secondly through orifices formed in various portions of the injector device, such as the bowl.
The bowl flares downstream so as to form a collar, and a deflector is placed around the collar of the bowl on the downstream side of the chamber end wall. The deflector forms a heat shield and it is cooled by the impact of cooling air coming from a plurality of perforations formed through the chamber end wall.
Examples of such turbomachine combustion chambers are described in patents FR 2 662 784 and FR 2 639 095 in the name of the Applicant.
The bowl is floatingly mounted therein to move in translation relative to the chamber end wall and to the deflector along a predetermined radial direction. Means are provided for guiding movement of the bowl in translation in the predetermined radial direction.
This configuration serves in operation to absorb the relative movements between the walls of the combustion chamber and the injector, which movements are due to thermal expansion differences between the chamber and the casing of the turbomachine.
Unfortunately, the collar of the bowl runs the risk of deforming as a result of the high temperatures that are reached in this region of the combustion chamber, such that the radial clearance that is needed between the bowl and the deflector can be disturbed and such that the injector can be moved off-center relative to the bowl, which leads to undesirable rotation of the sheet of fuel sprayed by the injector.